Method of forming concrete pilings using a reverse circulation drilling system

ABSTRACT

A method of boring a hole in which a down hole hammer is pneumatically operated to form a hole, and a cementous material is injected into the hole through a passage in the down hole hammer.

BACKGROUND OF THE INVENTION

[0001] The present invention is related to forming concrete pilings, andparticularly forming concrete pilings down hole, pneumatic, percussivehammer drilling systems.

[0002] Eccentrically mounted underreamers are known which include an armwhich travels in an orbit for underreaming operation, and which areretractable toward the hole axis for tool removal purposes. Other knownunderreaming equipment utilizes three bit mounted plates which areoutwardly displaceable, bit which incorporate a total working surfacewhich is substantially less than the perimeter of the bore. Suchundersized plates are subject to excessive wear and result in slowdrilling operation. Underreaming can also be achieved by use of a crownor ring bit, but components of those bits must be left in theunderreamed area when drilling is complete, which is costly andotherwise unacceptable in some drilling operations.

[0003] However, it remains a difficult task to form concrete pilings insoils wherein large rocks are dispersed in a relatively non-compactedsoil. As the percussive hammer is removed from the freshly bored hole,the dispersed rocks in the soil can be urged toward the hole, andprevent the filling of the entire hole with concrete as required forstructural integrity. In cases where a steel I-beam must be included inthe piling, the problem can be even more severe because the rockintrusion can prevent the insertion of the steel beam.

[0004] A need remains, therefore, for a method of forming concretepilings in soils having suspended rocks and boulders that using currentmethods, can intrude into the hole before the concrete and steel areinserted.

DESCRIPTION OF THE INVENTION

[0005] In my U.S. Pat. No. 5,511,628, which is hereby expresslyincorporated by reference into this application, I disclosed a pneumaticdown-hole drill with a central evacuation outlet. The apparatus of U.S.'628 permits continuous evacuation of large debris fragments through acentral axial bore formed in the bit and through a central evacuationtube attached thereto. Compressed air is directed downwardly throughperipheral channels, under the drill bit, and into a central evacuationtube. The flow of compressed air through the central evacuation tubeprovides continuous and efficient removal of earthen fragments from thebore, including rapid removal of fragments which would be too large forremoval through peripheral pathways along the casing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is a partial cross-sectional view of a drilling assemblyaccording to the present invention.

[0007]FIG. 2 is an expanded partial cross-sectional view of the assemblyshown in FIG. 1, showing the power head assembly, compressed air inletcollar, and the upper terminus of the dual wall pipe assembly.

[0008]FIG. 3 is an expanded cross-sectional view of the assembly shownin FIG. 1, showing the casing driver in greater detail.

[0009]FIG. 4 is an expanded cross-sectional view of assembly shown inFIG. 1, showing the dual wall pipe assembly and the box and back headassembly connecting the lower terminus of the dual wall pipe assembly tothe down-hole pneumatic hammer.

[0010]FIG. 5 is a cross-sectional view of the down-hole pneumatic hammerassembly, including the bit assembly.

[0011]FIG. 5A is a perspective view of an alternative design for thehammer barrel of the down-hole pneumatic hammer assembly.

[0012]FIG. 6A is an exploded perspective view of a first embodiment of abit assembly according to the present invention.

[0013]FIG. 6B is an exploded perspective view of a second embodiment ofa bit assembly according to the present invention.

[0014]FIG. 7A is a perspective view of the pilot bit on the embodimentof FIG. 6A.

[0015]FIG. 7B is a bottom view of the pilot bit shown in FIG. 7A.

[0016]FIG. 8 is a perspective view of an underreamer arm used in theembodiment shown in FIG. 6A.

[0017]FIG. 9A is an end view of the underreamer arm shown in FIG. 8.

[0018]FIG. 9B is an outer side view of the underreamer arm shown in FIG.8.

[0019]FIG. 10 is a bottom view of the bit driver of the embodiment shownin FIG. 6A, showing the axial surfaces which define the recesses whichreceive the underreamer arms, and the axial surfaces bear against theunderreamer arms to rotate the arms about the pilot bit for extensionand retraction.

[0020]FIG. 11 is side elevation view of the bit assembly shown in FIG.6B.

[0021]FIG. 12 an enlarged exposed view of the bit assembly shown in FIG.11.

[0022]FIGS. 13 and 14 are horizontal sectional views taken along line3-3 of FIG. 11 and showing the lower portion of the driver receiving theunderreaming arms with the arms shown extended and retracted;

[0023]FIG. 15 is a vertical sectional view taken along line 5-5 of FIG.13 showing a fragment of the driver bottom wall and an arm locking padthereon;

[0024]FIG. 16 is a vertical sectional view taken along line 6-6 of FIG.11; and

[0025]FIG. 17 is a perspective view of an underreamer arm.

[0026]FIG. 18A is a cross-sectional schematic view of the upper portionof a down-hole percussive apparatus that is adapted for practicing theclaimed method.

[0027]FIG. 18B is a cross-sectional schematic view of the lower portionof a down-hole percussive apparatus that is adapted for practicing theclaimed method.

DETAILED DESCRIPTION

[0028] Referring now to FIG. 1, a reverse circulation drilling system,shown generally at 10, includes a head assembly 11, a dual wall pipeassembly 12, and a down hole pneumatic hammer 13 within a bore casing14. Turning to FIGS. 2 and 3, head assembly 11 includes a casing driver15 for driving the bore casing 14 downwardly as the bit advances, and apower head assembly 16 of standard design for rotating the bore casing14 it is driven downwardly. Casing driver 15 includes an annular hammer17 which reciprocates vertically as compressed air is alternativelyadmitted to chambers above and below hammer 17. Hammer 17 impacts onanvil 18, which in turn impacts on casing cap 19. Casing cap 19 issealed against the inner surface of bore casing 14 to permitpressurization, through port 20, of bore casing 14 between casing cap 19and down hole hammer assembly 13. Pressurization of the casing providesa downward flow of air between the casing and the down hole hammer,preventing upward migration of debris between the down hole hammer andcasing, which can hinder the removal of the hammer. Power head assembly16 is connected to anvil 18 through linkage assembly 21 to impartrotation to the dual pipe assembly and the down hole hammer. Power headassembly 16 is of a design generally known in the field, other than itcentral member 22, which is threaded onto the upper end of dual wallpipe assembly 14, includes a central bore in communication with the dualwall pipe assembly to extend the debris discharge path through the powerhead to the elbow 29. The joint of central member 22 and the dual wallpipe 14 includes a port 23 for admitting air to the annulus 24 betweenthe inner wall 25 and the outer wall 26 of the dual wall pipe assembly.Collar 27 is mounted around the joint, and includes air inlet 28,through which compressed air is admitted into the dual wall pipeassembly for driving the down hole hammer as further described below. Anelbow 29 is rotatably mounted and sealed to the upper end of centralmember 22. Elbow 29, central member 22 and the inner wall 25 of dualwall pipe assembly 14 together form a central drilling debris dischargetube for continuously discharging drilling debris from the down holehammer as will also be described more fully below.

[0029] Turning also to FIG. 4, dual wall pipe assembly 12 is assembledfrom individual segments, each of which includes an inner pipe 31 and anouter pipe 33. Each segment includes a threaded male connector 33 and athreaded female connector 35 at opposite ends. Male connector 14 andfemale connector 15 each includes air ports 36 and 37 respectively whichare in communication with outer annulus 24 of dual wall pipe assembly11. At its upper end, dual wall pipe assembly is threaded in to centralmember 22 of power head 16. At its lower end, dual wall pipe assembly 11is connected to the box 38, which in turn is threaded into back head 40of down-hole hammer 13. Ports 42 an 44 communicate with annulus 24 ofthe dual wall pipe assembly to route compressed air therefrom into thedown hole hammer.

[0030] Turning now to FIG. 5, down-hole hammer 13 includes box 38threaded onto back head 40. A sleeve 41 and a hammer barrel 42 arethreaded into back head 40. A centrally located discharge tube 43 ispressed into sleeve 41. A wear sleeve 44 is fitted around hammer barrel40, and press fitted over ring 45 and onto shoulder 46 of back head 40.Sleeve 41 and barrel 42 define an annular upper air chamber 48. Centralevacuation tube 43 and barrel 42 define an annular lower air chamber 50.The lower end of barrel 42 abuts bit driver 52, and also includes aperimetrical lip 54 which engages wear sleeve 44 to center barrel 42 inthe wear sleeve. Hammer 53 is slidingly fitted into barrel 42 forreciprocation. Bit driver 52 is slidably fitted into barrel 42 belowhammer 53, and over the lower end of central evacuation tube 43. Bitdriver 52 is retained in barrel 42 by a plurality of keys 56, each ofwhich is fitted into a keyway 58 and annular recess 60 of bit driver 52.(See also applicant's U.S. Pat. No. 5,511,628, incorporated by referenceabove, for detail of an alternate barrel assembly incorporating a likekey and keyway assembly for mounting the bit driver in the hammerbarrel.) The key-keyway assembly permits the bit assembly to advanceahead of the dual wall pipe assembly during drilling.

[0031] Bit assemblies for use with the present invention are shown inFIGS. 6-10. In one embodiment (FIG. 6A), a bit assembly consists of abit driver 52, a pilot bit 82, and arms 88 a-c. Bit driver 52 includesan upper shank 83 having a recessed chamfer 84, camming surfaces 85 aand 85 b, and a lower portion 86. Lower portion 86 includes threeperipheral recesses 87 a-c. Hardened drilling buttons, preferably madeof a carbide material, are mounted on the peripheral and bottom surfacesof the pilot bit (Fig. 7). Arms 88 a-c are nested atop pilot bit 82, andslide thereon in an prescribed arcuate path defined by as will bedescribed. Each of the arms includes a raised boss 89 which is receivedinto corresponding recess 90 of bit driver 52 (FIG. 10). Raised boss 89serves several functions. First, impact forces from the hammer aretransmitted downwardly to the pilot bit 52 through bit driver 52, boss89, and arm 88. Second, boss 89 is received and retained in recess 90,where it rotates through a limited arc to extend and retract arm 88.With arm 88 in its retracted position, surface 91 is adjacent cammingsurface 85 a. in this configuration, the overall diameter of the bitassembly is less than the inner diameter of the bore casing, permittingthe bit assembly to be withdrawn from the bore. As arm 88 is rotatedclockwise about pilot bit 82 by clockwise rotation of bit driver 52,angled surfaces 85 a engage surface 92 and urge arm 88 outwardly. Therotation and extension of arm 88 continues until surface 92 a is abutssurface 85 b, and surface 92 b abuts surface 85a, locking arm 88 in itsextended position. To unlock and retract arm 88, bit driver 52 isrotated in the opposite direction. In its fully retracted position, theoverall diameter of the underreamer assembly is less than the insidediameter of the casing, permitting withdrawal of the entire underreamerbit assembly through the casing if necessary. This feature represents asignificant advance over known underreamers, which cannot be retractedand withdrawn through the casing if necessary.

[0032] In operation, compressed air is delivered into annular chamber 59through port 37, radial ports 60, annulus 62 and axial ports 64. In FIG.5, hammer 53 is shown during its downward stroke. Lip 66 is engaged withlip 68, sealing off chamber 48. Lip 72 is engaged with lip 74, sealingoff chamber 50. Port 78 is closed. As piston 53 continues downwardly,port 76 is uncovered, exhausting chamber 48. At about the same time, lip74 disengages from lip 72, admitting a fresh charge of compressed airinto chamber 50 to raise piston 53 to its upper position after it hasstruck bit driver 52. As piston 53 rises, port 78 is uncovered,exhausting chamber 50. Lip 74 engages lip 72, sealing chamber 50. Port76 is sealed by piston 53, and lip 66 disengages from lip 68, admittinga fresh charge of compressed air into chamber 48. The fresh charge ofcompressed air in chamber 48 drives piston 53 downwardly to beginanother stroke. The compressed air exhausted into ports 76 and 78 iscollected in port 80 (FIG. 5A), and discharged through the bit assemblyinto central evacuation tube 43, carrying with it drilling debris andearthen fragments dislodged by the bit. As an added precaution againstdrilling debris becoming lodged between arms 88 a-c and the pilot bit,in the bit assembly embodiment shown in FIG. 6B, port 91 is providedthrough which compressed air can be discharged to clear debris.

[0033] The flow of compressed air through the bit assembly isessentially continuous, and provides a continuous evacuation of drillingdebris from the drilling face of the bore. Moreover, the essentiallyconstant diameter of the evacuation tube and inner wall of the dual wallpipe assembly provides a constant air velocity, which further aidsdebris removal. The continuous removal of debris through the centralevacuation tube promotes continuous drilling. It is seldom, if evernecessary to stop drilling and raise the bit to clear debris from thebore. Significant improvements in drilling rates can directly result. Inaddition, it is possible to obtain a relatively accurate “core” samplefrom the bore which can provide useful information in both exploratoryand environmental applications.

[0034] An alternative bit assembly is shown in FIGS. 6B and FIGS. 11-17.The reference numeral 101 indicates generally the present drill bitassembly for attachment to the lower end of pneumatic down hole hammer.A driver at 102 includes a shank 103 of a diameter and splined forattachment to the percussive hammer. Integral with the shank is a driverhead 104. About head 104 are circumferencially spaced channels 105 forupward passage of earthen particles or debris. An axially extending bore106 of the driver receives a pressurized downward air flow for particleremoval. Head 104 is cross bored off center at 107 to receive pin 108engageable with a later described pilot bit of the drill assembly.

[0035] A lowermost surface 110 of the driver head 104 defines a seriesof cylindrical sockets 111 uniformly spaced apart and from vertical axisat A of the driver (FIG. 13). Each socket has a companion elongaterecess 113 formed in the lower portion of the driver to receive a limitstop pin of a later described underreamer arm. Additionally, lowermostsurface 110 of head 104 is provided with multiple arm lock pads 114 inthe form of downward projections which serve to lock each underreamerarm in an extended operative position. An internal wall of the driverincludes segments 116 and 117 which define an open area which receives acam block 118 and permits head movement thereabout. Irregular wallsurfaces, 116-117 alternately abut the cam block to limit driverrotation during arm positioning as later discussed.

[0036] A set of underreamer arms are indicated generally at 119 in FIG.12 with the following description of one arm applicable to all of thearms at 120 which are generally of angular shape in plan view. Withattention also to FIG. 17, an arm pivot post 121 seats in a socket 111formed in the underside of head 14 of the driver. A limit stop post orpin 122 of the arm projects upwardly into an elongate recess 113 in theunderside of the driver head 104 with an end wall 113A of the recesslimiting outward displacement of arm limit stop pin 122. Arm top andbottom walls are at 123-124 which both terminate outwardly in beveledarm outer edges 123A-124A, the lower beveled edge being provided withcarbide inserts or buttons 125. An inner side wall 126 of an arm 120moves about in relation to a later described cam block during armdeployment and retraction. A rearwardly beveled (relative arm rotation)arm end wall is at 127. Beveled arm edge 123A is engageable with thelower edge of a hole installed casing to contribute to inward armmovement during arm retraction at the end of a drilling operation. Anarm shoulder at 128 cooperates with the lock pads 114 on the driver whendeployed. The inner side wall 126 of each arm 120 travels along a wallsurface of the cam block during arm positioning.

[0037] A pilot bit is generally indicated at 130 and includes a mainbody 131 having an uppermost surface 132 on which is centrally locatedcam block 118 with walls 136. Integral with cam block 118 is a pedestal137 having an annular groove 138 thereabout to receive head carried pin8 in a tangential manner. Groove 130 is oversize to permit upwarddisplacement of driver 12 during arm positioning and subsequent lockingof the arms. A compressed air central passageway is at 139 of the bitand is in registration with driver air passageway 106. Spaced about thelower perimeter 131 of drill bit 130 are channel 141 through whichdebris flows upwardly past the arms during a drilling operation. Abottom wall 142 of the drill bit defines radially disposed air channels143 which are served with compressed air flows via internal passagewaysserved by axial passageway 139. The lowermost surface 142 of the drillbit is suitably equipped with tungsten carbide buttons or other wearresistant members 144 commonly used in earth drilling equipment.

[0038] In drilling and underreaming operation pilot bit 130 advancesinto the ground with the underreamer arms locked in a deployed positionbelow and radially beyond the advancing end of the casing at C. Casingmovement is facilitated by the relatively large underreamed area, and ifrequired, by the casing driver 15. In one embodiment, if the drill bitassembly advances more than a predetermined distance ahead of thecasing, linkage 21 operates a valve to provide compressed air to thepneumatic hammer 17 and associated porting casing driver 15.

[0039] At completion of the operation, the driver is partially rotatedin the direction opposite to drilling rotation to shift the arm pivotpins and specifically the arm inner ends along cam block walls 36 toretract each arm. Arm retraction is aided by the beveled arm outer edges123A engaging the bottom edge of casing C during retraction at the endof a drilling operation to permit removal of the drill bit assemblythrough the casing.

[0040] In operation with arms 53 a-c extended, exhaust air from thedown-hole hammer flows from port 42 through driver 51, arms 54 a-c,pilot bit 56, and into central evacuation tube 1 (FIG. 2), carrying withit drilling debris. Applicant's routing of exhaust air from thedown-hole hammer through the driver and into the underreamer assembly tocontinuously clean drilling debris from the underreamer assemblyrepresents a significant improvement in the drilling art.

[0041] Turning now to FIGS. 18A and 18B, the method of the presentinvention will now be described. The down-hole percussive hammer andunderreamer bit is shown generally at 1810. Assembly 1810 is operated toform hole 1820 as described above. Once hole 1820 is formed, valve 1830is closed to isolate the central channel 1840 from the vacuum unit (notshown). Concrete is then pumped into central channel 1840 through inlet1850. Low-pressure air is also introduced into through air inlet 1860 toslightly pressurize casing 1870. Once the concrete has filled centralchannel 1840, the casing is slowly removed from the bore as moreconcrete is pumped into central channel 1840. The concrete flowsdownwardly through central channel 1840 and out through bit 1880 intothe bottom of hole 1820. A small spacer 1890 is mounted onto the bottomof bit 1880 to keep it spaced above the concrete surface to ensure aflow path for the concrete into the hole. The low-pressure air providesa pressure in the casing to resist intrusion of the concrete into thehammer and casing. The lift rate of the casing is matched to.the fillrate of the concrete, thereby filling the hole with concrete as thehammer and casing are removed, and preventing the intrusion into hole1820 as discussed above. In this way, and uniform concrete piling can beformed nearly simultaneously with the boring of hole 1820, resulting ina much more reliable and strong piling, and a more cost efficient methodas well.

[0042] In an optional following step, after the hammer and casing havebeen removed and the hole filled with concrete, a structural I-beam canbe inserted into the uncured concrete using conventional driving andvibrating methods.

[0043] The foregoing description of the invention is intended to beillustrative rather than exhaustive. Those skilled in the art willappreciate that numerous changes in detail are possible withoutdeparting from the scope of the following claims.

1. A method of boring a hole: providing a down hole hammer comprising adriver; a pilot bit rotatably coupled to the driver, the pilot bithaving a shank, a peripheral drilling surface, a lower surface, and abore extending from the lower surface generally upwardly through theshank; a plurality of underreamer arms rotatably mounted intermediatethe driver and the pilot bit and including underreaming surfaces, theunderreaming arms having an extended position wherein the underreamingsurfaces are positioned concentrically outside the pilot bit perimeter;cam surfaces engageable with the underreamer arms for urging theunderreaming arms into their extended positions, for locking theunderreaming arms into their respective extended positions, and forretracting the underreamer arms responsive to rotational movementbetween said driver and said pilot bit; and surfaces defining at leastone air passageway between an outer surface of the driver and the borein the pilot bit; the least one fluid passageway in communication with asource of a cementous material and at least one said cam surface, andfurther including a valve operable to discharge the cementous materialto said at least one cam surface; operating the downhole hammer to borea hole; and, discharging cementous material into the hole.
 2. A downhole hammer comprising: a driver; a pilot bit rotatably coupled to thedriver, the pilot bit having a shank, a peripheral drilling surface, alower surface, and a bore extending from the lower surface generallyupwardly through the shank; a plurality of underreamer arms rotatablymounted intermediate the driver and the pilot bit and includingunderreaming surfaces, the underreaming arms having an extended positionwherein the underreaming surfaces are positioned concentrically outsidethe pilot bit perimeter; at least one cam surface engageable with theunderreamer arms for urging the underreaming arms into their extendedpositions; surfaces defining at least one air passageway between anouter surface of the driver and the bore in the pilot bit; and, theleast one fluid passageway in communication with a source of a cementousmaterial and at least one cam surface, and further including a valveoperable to discharge the cementous material to the at least one camsurface.
 3. A downhole hammer according to claim 2 further comprising:the at least one cam surface including at least one surface for lockingthe underreaming arms into their respective extended positions.
 4. Adownhole hammer according to claim 2 further comprising: the at leastone cam surface including at least one surface for retracting theunderreamer arms responsive to rotational movement between said driverand said pilot bit.